Animation Nodes: Is it possible to instance nested instances?
Unfortunally the Object Instancer does not work in subprograms, because node it has to monitor the scene to keep track of a specific set of objects. It's very similiar to the Separate Text Object node.

There are two main ways to work around that:


Calculate the number of objects you need and create that many before the loop starts. For a simple grid there is also a template:


Make the first row of instances using AN and then use the array modifier like I did in this audio animation:



For that the source object needs an array modifier and you have to activate Copy Full Object in the Object Instancer node so that the modifiers are copied to the instances as well.




[EDIT]:

I just created a node tree that does parts of what you want to archieve. You may be able to use it as a reference:





Basically I use approach 1. here. The first loop splits the long object list into multiple shorter lists with equal length. The second loop calculates the positions of the objects.